The present invention relates to a cord lock for a venetian blind or a shade, such as a pleated shade, and more specifically to a lock for the lift cord of such venetian blind or shade.
Different forms of such cord locks are known in the art, as for example disclosed in U.S. Pat. Nos. 4,180,118; 4,245,688; 4,352,386; and 4,476,909. They have stationary pulleys made from either plastic material or metal, and are either rotatably mounted or are fixed in a housing, and also have a floating serrated or knurled rivet which can move up and down in slots in the housing. The lift cord lifting and lowering the blind or shade passes between the pulley and the rivet. When the lift cord is to be locked in position the rivet engaged by the cord travels upwardly with the cord, caused by the weight of the blind, and the cord becomes wedged between the rivet and the pulley. When the cord is pulled downwardly the rivet drops away from the pulley and cord, and the blind or shade is released.
It is intended that the rivet gently moves the lift cord against the pulley thereby locking it in place, when the blind or shade has been raised or lowerd to the desired position, and the lift cord is released. It must be assured that the cord lock operates in a "crash-proof" manner, i.e. that it maintains the blind or shade in the locked position so that it does not come crashing down.
It is an object of the present invention to provide a cord lock for a venetian blind or shade, in which both the firmness and sensitivity of the cord lock is increased without jeopardizing the "crash-proof" feature of the cord lock.